On Thu, 2009-02-05 at 20:46 +0100, Lennart Augustsson wrote:
You are absolutely right. The statement "The values of the IO monad are programs that do IO. " is somewhat nonsensical. Values don't do anything, they just are.
Technically, programs don't do anything either. I think of values of type IO a as being --- conceptually --- arbitrary sequences of machine code instructions. Just like a sequence of machine code instructions can be stored away in /bin/cat, and not do anything, an IO value needn't do anything, either. Until it's stored in memory and the instruction pointer set to its first instruction. At which point, if you want to get really picky, it's still the CPU doing things. Which it is told to do by its fixed microcode. Which tells it to look at your program to see what to do. Which = looking at the `value' of your IO-typed expression to see what to do. jcc